We ran a negative pressure on our circle track engines by having a tube with baffles in it mounted to the factory fuel pump location. Can't get any closer to the oil supply than that but never a wisp of blue smoke. Rather than engine vacuum, which wasn't much with both valves open most of the time, we had a tube in the exhaust collector with the end angled so the high velocity exhaust passing over it drew a high vacuum. Baffled tube was about a foot long, vertical, and at least eight overlapping baffles at a 45* angle. Early sbc had a baffle (they called a condenser) in the lifter gallery that was simply a smaller tube inside a larger one. It doesn't take much to draw air and not liquid/vapor but a bit of thought to do so. For sure, you and the whole neighborhood will know if it's wrong.
I’ve seen some kits you can buy that use exhaust to pull the PCV circuit.
